Sustaining rotor for aircraft



Sept 5f, 14939. r.' 'rHEoDoRsEN Erm. 2,172,334

SUSTAINING ROTOR FOR AIRCRAFT i 1 'Filed Nav. 27, 1936 5 Sheets-Sheet se-Pt- 5, 1939. jHl-:onRsEN Er AL l .2,172,334

SUSTAINING ROTOR FOR AIRCRAFT Filed NOV. 27, 1936 5 Sheets-Sheet 2 MMIV 111,111,119 /lg 1, r

7///\ Il! 2a NM Sept. 5., 1939. 'r.THEoDoRsEN Erm. 1 2,172,334

v SUSTAINING KOTOR FOR AIRCRAFT Sept. 5, 1939. v T.' rHEonoRsEN er AL l2,172,334

` v SUSTAINING KOTOR FOR AIRCRAFT Filed Nov. 27, 193s 5 sheets-sheet s f//A/ NME Patented Sept. 5, 1939 E y l y UNITED STATES PATENT oFFIc-E 2,172,334 SUSTAINING RQTOR FOR AIRCRAFT Theodore Theodorsen, Hampton, Va., and Edward F. Andrews, Chicago, Ill.

Application November 27, 1936, Serial No. 112,888 3'7 claims. (Cl. 244-17) This invention relates to sustaining rotors for guides on the drum. It also conduces to stable aircraft, and particularly to sustaining rotors operation, Further, if the structure is used as having blades composed of a large number of seca helicopter, this rigidity operates to impart stifftions hinged together on axes generally parallel ness to the blade in the plane of the torque.

5 to the chord of the blades so that they may be It is also desirable that the blade, at a point Wound up around a polygonal drum for storage near the hub, be permitted a certain degree of in compact compass when out of operation or freedom to yield under periodic strain in the when only 'part of the blades is being used. The plane of its chord. This freedom should be presrotating wing system of this invention may be ent when the wing is being wound or unwound,

lo driven by air forces as an autogyro, or by power or when in operation in a partly unwound conl applied to the blades as a helicopter. 'Ihe indition as Well as when fully extended. To atertia of the rotating blades may be used to effect tain this desirable condition While-preserving the the Winding up of the blades around the drum. advantage of a wing which is rigid in the plane This invention relates to a special type of coilof rotation and which Will wind up upon the drum l able rotating, wing generally described and without skewing with relation thereto, the drum l5 claimed in our copending application, Serial No. as a whole is allowed to pivot in a generally hori- 9'?,804, filed August 25, 1936. t zontal plane.

Thisgeneral type of wing is flexible and rela- 'Ihe structure disclosed realizes to a large detively nonresonant and, during rotation, the lift gree the aerodynamic and other advantages of 2G of its blades is balanced by centrifugal force. In the coilable rotating wing with a largemeasure 20 normal operation the wing is rolled up into a coil of torsional stiffness per unit of .weight and with of relatively small diameter before its rotation a. relatively simple and inexpensive construction. ceases. Y This structure permits simple and effective means lThe improved coilable rotating wing herein for winding and unwinding the wings, for providdescribed and claimed, is of this general type, ing for their rotation,;.both mechanically and 25 but is characterized by a high degree of rigidity under the influence of air forces, and for inclinin the plane of its chord, and by a high degree of ing the axis of rotation of the wing system as a torsional rigidity tending to hold the chord of whole relative to the aircraft for the purpose of the entire wing in fixed relation to the axis' of control.

rotation. To provide this rigidity in a wing with Other desirable characteristics,advantages and 30 many joints, vthe play in the joints and the change capabilities ofthe invention will appear from the of angle resulting therefrom should be reduced following description of a preferred embodiment as far as possible. To attain that object, itis thereof taken in conjunction with the accompreferred to make the hinges between adjacent panying drawings, in which sections as long as possible and preferably prac- Figure 1 is a fragmentary elevation of an air- 35 tically coextensive with the chord of the blade. craft embodying our invention;

Preferably, the sections are in the form of hol- Figure 2 is a plan View partly in section, the low, rigid elements, and a large number of indisection being taken on the line 2-2 of .Figure 1; vidual hinge elements are provided at close in- Figure 3 is a sectional view on a larger scale,

40 tervals along the chord of the section to provide taken on the line 3-3 of Figure 2, and showing '40 a uniform distribution of tension and other forces the manner in which the Wing is controlled; to the walls of the section. The adjacent wing Figure 4 is a sectional ViewI taken on the line sections being pivoted together substantially in 4-4'of Figure 3;- the line of the chord, the Wing is extremely flex- Figure 5 is a sectional view on a larger scale,

ible in the direction of `its thickness so that it taken on the line 5-5 of Figure 1, showing the 45 mayyield in a vertical direction to the air forces manner in'which the drum is mounted and drivunder the restraining influence o f centrifugal en; force while being stiff in the plane of itsvchord Figure 6 is a sectional view-through the drum, and can be wound up around the drum with itsl taken on the line 6 6 of Flgure 5;

.J0 chord parallel to the axis of the drum. Figure '7 is a sectional detail of the drum, taken 50 This rigidity in afore and aft direction or in 0n the line 1-'7 0f Figure 6; y the plane of the chord is advantageous in that Figure 8' iS 2f Sectional View thrllgh the Wing it insures that the wing will wind up on the drum in Wound up condition the view being taken on with one layer directly on top of the other withthe line 8-8.of Figure 1 and being on a substanout skewing and without the necessity of any tially larger scale; 55

Figure 9 is a sectional detail viewtaken on the line 9-9 of'Figure 8, showing the manner in which the blade bends when wound up;

Figure 10 is a similar sectional view showingy Figure 15 ispan end view of an inner sectionl shown in relation to an outer section;

Figure 16 is a sectional view through a modi# ed form of drum; and Y Figure 17 is a plan view of an aircraft embodying my invention. i

Referring to the accompanyingdrawings, the reference numeral 26 designates thefuselage of an aircraftjwhich includes an engine 2|, propeller' 22 and tail ||9. The supporting rotor comprises two Vwings 23 which are shown in Fig-V ure 1 wound up upon drums 24. The drums 24 are carried by arms 26 extending outwardly from a rotatable hub or housing 26. As best seen in Figure 3, the rotatable hub or housing 26 is mounted by means of bearings 21'upon a swinging member 28. 'Ihe swinging member 28 is provided with trunnions 29 which are rotatably mounted on the ring member 36. "The ring member .36 isv provided with trunnions 3| located at right-angles to the trunnions 29, and the trunnions 3| have bearings in-I members 32 which are rigidly mounted on the fuselage by means of -the struts 33.

'Ihe swinging member 26 rigidly carries a depending tubular member 34, to ,the lowerl end of which a yoke is pivotally connected by pi-ns 36. 'nie yoke 35 carries a'pin 31 having an axis at right-angles to the axes/,of the pins 36.

On the pin 31 is pivotally mounted a head 36.

which `is rigidly connected to a rod 36. The rod 39 'has a telescopingv fit in a tubular member 46. The tubular member 46 is mounted for universal movement so that it can be moved inany` in` any direction desired for control of the air.

craft, The member 26 swings freely in anydi rection,` owing to the universal mounting/pro'- vided by the trunnions l29 and 3|. l

The, hub 26 serves as a housing for helical gear 44 which is rigidly carried by a shaft 45 which extends through the center of the member 28.

t its lower end the hub 26 has-rigidly mounted ,thereon a gear 46 which is in mesh with a pinion 41. The pinion 41 is driven from the engine 2| through a shaft 48, a shaft 49 which can be engaged with the shaft 46 by means of a manually` operated clutch '56. beveled gears 5| and shaft 52 which is connected to the beveled gearing 6| and th pinion 41. by means of. uni-- verm joints 53., The shaft sz is spurred into the lower member of the upper universal joint ,53, to permit the free movement of the mem-j ber 28.

VBelow the gear 46, the shaft has rigidly mounted thereon a pinion 54 which meshes with planetary gears 55 which are rotatably carried on the under side of the gear 46 and which mesh lwith the internal gear 56. Internal gear 56 is mounted for free rotation on the lower part of the shaft 45. It includes a cylindricalportion 51 which serves as a brake drum and is adapted to be operatively engaged by means of a brake band 58,. Below the brake drum 51 the shaft `45 'has rigidly mounted thereon a brake drum 59 which is adapted to be engaged by means of a brake band 66. The brake bands 58 and 66 may be contracted alternately by -suitable actuation of a shaft 6| in one direction or the other.

The shaft 6| extends through the tubularmember 34 and carries at its lower end a hand wheel 62. At its upper end the shaft 6| carries cams 63 and 64 whereby said brake'band 56 0r 66 may be applied as desired.

'I'he helical gear 44 engages gears 65 which are located in lateral extensions 66 of thehub 26. The tubular arms 25 extend two opposite spiral.

outwardly from the extensions 66 in opposite di- -gear 16.is rigidly mounted on shaft 12 .which extends througha hub member 13 which is integral withthehousing 1|, as best. seen in Fig- `ure l5..

The hub member 13 is provided witha slot 1 near its extremity remote from the gear 10, and' in this slot is located' a gear 15 having a spherical face. Thisv gear is keyed to the shaft 12 so as to rotate therewith. At the locationl of the gear 15 the hub member 13 is provided with up@ wardly and downwardly directed trunnions 16, the 'axis of4 which is at right-angles to the axis of the shaft 12. The axis of the trunnions 16 lies in the medial plane of the gear 15.

The gear 15 meshes with two gears 11 which r are rotatably mounted in a hub 16. The gears 11 have toothed edges of concave formation to adapt them to cooperate with the spherical gear 152 The hub 16 has openings on its upper'and -lower sides -for the reception of the trunnions 16, and the gears 11 operate in Openings 19 in -the sides of the hub 18, as best seen in Figure 6.-

At its inner and outer ends the hub 18 carries, by means of bearings 86, lthe drum 24. The drum 24 is a. hollow member provided at an in-` termediate position with an internal ring' gear 8|. The ringfgear. has teeth which are convex in form and engage the gears 11.

. It will readily be understood that when the shaft 12 is rotated the gears 11 are likewise rotated, owing to the fact that the hub 18 on which tation by the trunnions 16. yAs a result of the rotation of the gears 11, the internal gear 6| of the drum 24 is rotated in a direction opposite to the direction of rotation of the shaft 12'.

It will be noted that the drum 2 4 and the hub '|18 can swivel in a substantially -horizontal direction with respect to the shaft 12 and the hub 13,

the spherical gear. 15 permitting such swinging.

they are pivotally mounted is prevented from ro- Damping means, which will hereinafter be more fully described,-are preferably provided to lessen and decrease movements or vibrations of the drum about the trunnions 16.

It may here be noted that the spiral gears 6 and 10 are non-reversing so that the centrifugal force of the wings has no tendency to unwind the blade from the drum. Consequently, the device is self-locking, and all that needs to be done is to feed out any desired length of wing, and when sufficient has been extended it is merely necessary to stop the drive of the drums vto maintain the extension of the wings unchanged.

The manner in which the blades are unwoundis as follows: The engine 2I being in operation, the clutch 50 is engaged, with the result that the hub 26, together with the dums 24 carried thereon, are caused to rotate bodily around the axis of the hub 26, the drive being effected by gears 41 andv 46. The hand Wheel 62 is then rotated so as to cause the brake 58 to engage. This brake is'preferably arranged to impede the movement of the drum 51 and the internal gear 56 but preferably it is not strong enough to lock these elements against rotation under heavy resistance.

AThe result of the slowing up of the internal gear 56 relative to the gear 46 is that the planetary gears move relatively to the internal gearv and drive the shaft 45 at a higher speed. Before the application of the brake 58 the shaft 45 rotated at the same speed as the hub 26. When it is rotated at a higher speed it causes the rotation of the drums 24 in a direction to extend the blades'. The centrifugal force of the blades tends to move the projected portions outwardly in a radialdirection.l

If the brake 58 remains engaged for a sufficient period, the blades will be extended completely. Owing to the slippage of the brake 58, the blades will not be rewound in the opposite direction.

They will remain in their full extended position and the drum 51 will merely slip relatively to the brake 58. The brake 58 should, however, be disengagedwhen the blades are fully projected. If it is not desired to project the blades to the fullest extent, the brake 58 is disengaged vwhen the desired extension of the blades is attained and,

owing to the non-reversing characteristic of the spiral gears 68 and 10, the drums 24 are automatically locked and the centrifugal force of the blades is unable to effect further extension of the blades. The brake 58 may also be used to retard the rotation of the assembly, if desired.

If the rotor is intended to operate asan autogyro, the clutch 58 is disengaged and the rotor assembly is maintained in operation by the air forces. If, however, the rotor is intended to opcrate as a helicopter, the power drive is maintained.

When it is desired to wind the blades up on their drums, the hand wheel 62 is rotated so as to apply the brake 80 to the drum 59. When this is done the shaft 45 is arrested, likewise, the helical gear 44. The spiral gears 65 are carried around the helical gear 44 and are caused to rotate about their axes by their meshing engagement with the gear 44. This results in the rotation of the shaft 68 and the worm 69, with the result that the drums 24 are driven so as to wind upthe blades thereon. The winding up of the wing may be arrested at any time so that any desired length of wing may remain effective.

Normally, the wings are-fully extended for landing, and after landing the brake 60 is applied to wind up the wings.l When this is done the air-4 craft has a large ground stability and resists any tendency to overturn.

The trunnions 29 and 3l, which provide for the universal mounting of the rotor upon the aircraft, are located on substantially the same level as the axes of the drums 24. The result is that when the blades are fully extended their inner ends are v substantially in alignment with the universal joint, and the rotor as a whole may be adjusted by hand by means of the lever 4I with the application of relatively small force.

The outer end of the hub 13 is provided with an extension |09 to which is pivotally mounted a link IIU. The linkv III) is pivotally connected to the rod I I I of apiston I I2 ofa dash-pot II3. The dash-pot II3 is rigidly mounted on the hub 18, and the rod III extends through an opening II4 in said hub. The piston |I2 is provided with a metering orifice I I5 which can be made of any desired size. It will readily be understood that the dash-pot I I3 serves as a damping means to damp swinging movements of the drum with respect to the hub 13, that is, movements resulting from the swinging of the hub 18 about the trunnions 16 carried by the hub 13.

It will be understood that the air resistance of the rotor should bekept as low as possible, particularly where lhigh speed performance is desired. For this purpose the drums24 may be reduced in size so that they offer little air resistance whenV the blades are fully extended. The drums supporting arms 25 and the general supporting structure of tlie rotor may be streamlined in any suitable manner so as to reduce air resistance.

It will be understood, particularly with reference to Figure 2, that the axes of 'the drums 24 are not parallel since they extend upwardly in the direction of rotation so as to locate the forward edge of the blade above the trailing edge and provide the angle of incidence necessary for aerodynamic support.

The drum 24 is preferably polygonal in cross- 4 section. As seen in Figure 6, it may be substantially hexagonal, departing from a true hexagonal section, merely to provide for the securement of the inner blade section thereto. For this purpose one of the sides of the polygon is provided with a boss 82 which is provided with .a plurality of slots 83. The slots 83 receive perforated triangular-shaped tabs 84 which project from one end of the innermost section 85 of the blade. A rod 86 extends through aligned open- `ings inthe boss82 and tabs 84, being secured in position by means of a washer 81 and cotter pin 88.

It is to bevunderstood that the hinge pin 86 is parallel to the axis of the drum 24 and hub 18. Consequently, the extended wing, being rigid against torsion, maintains its angle of incidence. The hub 18 being free to move on a. generally vertical axis with respect to the shaft 12 and supporting hub 13, but being rigidly held against relative movement on a horizontal axis, the angle of incidence of the blade is maintained notwithstanding the degree of freedom between the drum 24 and the supporting hub 13.

Referring to Figure 1, it will be readily understood that the sections of the blade are of approfpriate length to enable the whole blade to be wound 'up on the drumsy 24. increasing size of the hexagon with each added layer of wing Wound thereon, the sections are made longer in each successive layer outwardly from the point of attachment.

Because of the` We prefer to u make -the blade sections of metal, with a high ratio of strength to weight. y

In one manner of makinga blade section, a piece of metal is stamped so as to provide adjacent deformations"corresponding to the upper wall 89 and the lower wall 90 (Figurev) of the 'desired air foil section, and also to provide end wall portions 9| and 92 adjacent the upper and l lower walls 89 and 90. The two portions are bent around the forward edg e 93 so as4 to bring the "end wall portions 9| and 92 into contact and to bring the two' extreme ends of the piece of metal into contact to provide the trailing edge 94.

The assembly of the box-like structure which constitutes the wing section is completed by welding along the lines 95 between the abutting edges of the wallv portions 9| and 92 and along the trailing edge 94. Before the welding is done the other elements of the wing section are installed. Thus slots 96 are cut in the end wall portions 9| and 92 and a strip of metal 91,

corresponding in shape tothe end walls of the section, is inserted adjacent the end wall portions 9| and92. i

The strip 91 has struck -up therefrom the. metal tabs- 84which are of generally triangular form and are provided with central openings 98 for the reception of the pivot pin 86 or pivot pins 99 between adjacent sections. The tabs 84 are located, of course, so that they register with the slots 98 in the end wall portions 9| and 92. The

strip 91 may be secured to `/the adjacent wallv portions." and 92 by any suitable means, for

example, byspot-lwelding.l It may here be noted that a large numbe'r of closely located tabs 84 are 4provided and that they extend as near as possible to the front and rear ofthe sections so as to provide a hinge with a high resistance to torsion and to distribute the strains over the whole section.

'I'he blade sections are wound up on the drum in the manner shown in Figure 8, from which it will be seen that the superimposed wing sectionsl contact each other in a plane which is substantially at right-angles to the axis of the drum'. We reinforce the' wing sections against v crushing when .being wound or unwound by providing in this plane reinforcing members which may be in the form of a strip of metal j having its edges .turned to provide a U beam structure. The edges of the U beam structure'l00 along the length thereof are' secured, for example, by

spot-welding tothe upper and lower curved surfaces of the air-foil section. Theend flanges of the reinforcing member |00 may be secured by welding or otherwise to the reinforcing strips '91. By providing thereinforcing members .|90

substantially in the only plane in which there i when the same is rotated. 4A vfurther eifect of the longv hinge is to reduce to aminimum the `change in angle of the wing from root to tip with any given amount of play in the joints when subject. to torsion. Thus, the angleof the whole blade maybe held -close to the `angle desired by the torsional stiffness andthe angle at which the drum, to which the wingeis., attached, is

lmounted with relation to the-*axis of rotation of the whole wing system. y l A The outside covering of our improved wing section, that is, the Walls 89 aand 90, performs three functions. In the rst place, they serve as tension members taking most of the tension of the extended wing, which tension is distributed by the long hinge and closely spaced tabs 84 substantially over the whole area of the covering; secondly, they serve to resist torsion in the wing; and finally, they serve asthe outside cover -of the wing section.

Adjacent wing sections are `pivotally secured together by means'of pivot pins 99 which pass through the aligned openings 98 in the adjacent tabs 04 of the adjacent sections. Figure 12, the hinge pin 99 may be secured against longitudinal movement by a head |0| at one end and collar |02 and cotter pin |03 at the other end. I

The holes 98 in the tabs 83 may be made to taper outwardly from the section carrying them. as shown in Figure 14. As a result of this construction, the tension of the blade tends to locate As shown in the pin 99 rmly inthe outer reduced ends of the l openings 98 so that even after considerable wear there will be no loss of torsional rigidity when the blade is in use. The centrifugal force exerted on the rotating blade keeps the pins 99 firmly against the reduced portions of the openings 98 and takes 'up any tendency of free play between adjacent sections around the longitudinal axis of the blade.

Another means for taking up any free play around the axis of the blade between adjacent sections is shown in Figure 13. In this structure the openings 98 inthe tabs 84 are of graduated size and the hinge pin 99 has a corresponding taper so that it will fit snugly into the openings. The head |0|' of the pin'99 is displaced from the nearest `tab 84 so as to provide for a limited longitudinal movement of the pin 99 to take up wear.

' The collar |02 provided at the other end of the pin isl spaced beyond the adjacent tab 84, as shown in Figure 13, and a spring |04 is located between that collar and said tab.

It will readily'be understood that the spring |04 keeps the hinge pin 99 in firm contact with all the aligned openings in the tabs 83 so that a torsion-resistant hinge joint is provided.

The blade sections can be fabricated in otherl ways` than that described above. For example,

as shown in Figure 14, an end wall |05, with.

hinged lugs attached, formed-of a single piece,

may be provided which is welded around its periphery toA the 'top wall 89 and bottom wall 90.

The top wa1 l,89 and bottom Wall 90 may be' formed of a single sheet of metal bent to the proper shape and welded along the trailing edge 94 to complete the section.

We prefer to ll in the open spaces around the hinge elements and between the adjacent wing sections with readily compressible material.

This vfilling may suitably be provided by two pieces |08 of molded sponge rubber, which are formed to correspond to the ends of the sections between which' they are placed. The pieces l|06 are, of course, formed with recesses tov accommodate the hinge pin`99 and with slots through ',which the tabs 84 project. Each 'piece |06 is secured by cementing to an'end of a wing section,

the tabs' 84 projecting into the slots provided therein. The sections .are then placed end to end so as to bring the openings 98 in the tabs 84 into alignment, and the pin 99 is projected between the two abutting pieces |06 of rubber into the aligned openings.

Owing to the ready flexibility 4of the sponge lrubber it may be pushed out of place to facilitate the entrance of the hinge pin 99 and the application of the collar |02 and cotter pin |03 and, in the case of the embodiment shown in Figure 13, the spring |04. yWhen the wing is extended the two pieces |06 of sponge rubber are in the relation shown in Figure 10, and they provide smooth surfaces which are continuouswith the surfaces of the adjacent sections. When the wing is wound up upon the drum 24, the lower portions of the pieces |06 are compressed, as shown in Figure 9. l

'Ihe sponge rubber of which the pieces |06 are formed may be relatively dead so that the pieces absorb energy and dampen any vibrations in the wing in the plane ofthe axis of rotation. Other means for absorbing energy may be used for that purpose, if desired.

When the wings are fully or partly extended, they are held outwardly in the radial direction by centrifugal force. They are wound upon the drum against this tension. It is preferred that the outer sections of the wing shall tend to hold the free end of the wing against the drum so that if the drum continues to rotate after the wing is completely wound up it can do so without damage to the wing tips. This may readily be effected by providing suitable springs between adjacent-sections in the tip of the wing. Thus, as

shown in Figure 9, a spring or a suitable number of springs |01 may be provided in the hinge joints toward the wing tip. The spring |01 may have a central loop through which the hinge pin 99 passes, and it may have two arms |08 which extend upwardly and bear against the end walls of the adjacent wing sections.

. As will readily be understood from Figure 9, these springs tend to move the adjacent Wing sections into angular arrangement corresponding to their wound-up relation. As a result of these springs, the outerlayer of the wound-up blade is resiliently held toward the drum.l When the rotor structure is driven, as hereinbefore described, for the purpose of projecting or extending the wings, the centrifugal. force due to rotation overcomes the action of the springs |01 and the adjacent sections move into the relation shown in Figure 10 as they clear the drum.

'I'he springs |01 are also inclosed Within the pieces |06 of sponge rubber which are formed with openings to receive them.

It must be understood that the torsion increases inwardly along the Wing and is greatest near the drum. We may make special provision near the drum to provide longer hinges near the drum. Thus, as shown in Figure 15, the innermost sections or layer of wing sections 85 may be made larger than the outer sections 85 to provide to some extent in the interest of strength and resistance to.torsion near the hub. u

While we have shown two wings 23, it must be understood that a greater number may be employed, -if desired. 'As best shown in Figure 8, we prefer to decrease the thickness of' the sections in the'outw'ard direction of the blade. This decrease may be gradual along the blade or it may be attained by the employment of transition sections, as shown in Figure 1.

'I'he embodiment of drum shown in Figure 16' shows a preferred streamlined form. In this embodiment the hub 18 is foreshortened and the shaft 12 is connected to the drum 24 by means of a universal joint member |20. 'Ihis universal joint member may comprise two cross pins I 2| and |22 pivotally mounted in bearings on members |23i'and |24, respectively. The member |23 is carried on the end of the shaft 12. The member |24 carries a stub shaft |25 splined into a boss on the drum 24. It is to be noted that in this embodiment the drum 24 rotates in the same direction as the shaft 12 and consequently the shaft 68 must be driven in a direction opposite to that of this shaft in the first described embodiment in vorder to drive the drum in the same direction. In this embodiment of drum structure the 4axis of the trunnions 16 is displaced from the plane at right angles to the shaft 12 to an extent to render this axis parallel to the axis of the hub 26 about which the structure rotates.

We may provide weights |21 in the o utermost sections of the wings. Theseweights accentuate the centrifugal force of the Wing and may be used to balance the wing. For this purpose they are preferably located adjacent the forward edge of the wing and have a tendency to bring the centers of gravity forward towards the aerodynamic centers of the wings.

Although the invention has been described in connection with the specific details of a preferred embodiment thereof, it must be understood 'that such details are not intended to be limitative of the invention except in so far as set forth in the accompanying claims.

We claim:

1. In combination, a rotating aircraft wing, a drum to whichthe inner end of said wing is fastened, said wing having hinges at a pluralityA I of the wing is attached for winding thereon.'

3. In combination, la rotating aircraft wing composed of a number-of rigid sections hinged together near the leading edge and the trailing edge to permit the Wing to bend in the plane of its thickness, and means for forming the wing into a compact coil for storage.

4. A rotating wing system for aircraft comprising a hub, a drum carried'by said hub, a wing composed of a plurality of rigid sections hinged together near their leading and trailing edges attached to said drum so as to be rigid therewith in the plane of the chord, means for pivoting said.drum so that ,the wing and the drum move forward or backward in the plane of the chord, and means for rotating said drum to wind up said 'wing therearound.

5. I n combination, a wing storage drum, a wing attached thereto, means for pivotally supporting 76 said drum so that it may move with the wing attached thereto in the plane of the wing chord, and means within said drum for causing it to rotate and wind up the wing around it. l

6. In combination, a wing storage drum, a wing hinged to bend in the direction of its thickness but rigid in the plane of its chord attached thereto, pivot means within said drum about which said drum and said wing may pivot in the general plane of the wing chord, and means for Winding said wing around saidvdrum for storage.

7. In combination, a wing storage drum, a multiple-section wing attached thereto, adjacent sections being hinged together near the front,

, near the middle and near the rear of the wing chord, and means within said'drum for rotating it to wind up said wing thereupon.

8. A rotating wing system for aircraft comprising a hub, arms carried by said hub, drums carried by said arms, torsionally rigid hinge jointed Wings carried by said drums, and means carried by said hub and said arms for rotating said drums to wind up said wings thereupon.

9. In a rotating wing for aircraft comprising a plurality of rigid sections'hin'ged together, a

thin metal shell of air foil contour forming the surface of each section, an vend plate attached to each end thereof, a plurality of hinge lugs extending outwardly from said end plates at intervals alongthe chord of said wing from front form a hinge connecting adjacent sections, and

a stiffening member extending through the section' from one end to the other and from the bottom surface to the top surface substantially at the thickest point of the wing section to prevent said sectios from deforming when wound up into a coil.

10. In a rotating wing system,'a drum, a wing rigid in the plane of its chord and against torsion but hinged on a plurality of parallel axes to bend in the direction of its thickness, and means securing said wing to said drum rigidly in the plane oi the wing chord and for pivotal movement on an axis parallel to said axes and in the plane of the wing thickness. 11. In combination, a wing comprising a plurality of rigid sections pivotally Iconnected in series on parallel axes to permit the wing to be wound up into a coil, said sections each comprising a hollow body o'f airfoil contour, and a stiffening web in each section 1in the plane of contact between the sections when the wing is coiled up.

12. In an aircraft, a rotating wing assembly, a non-rotating member supporting said assembly, 'a

`1`iniversal joint connecting saidnon-rotating member t'o said aircraft, a hub carried by said assembly, a plurality of wing storage drums mountf ed upon said hub, flexible wings attached to said drums and adapted to be extended from and* wound up around -said drumsy by the rotation` thereof, the axes of said drums lying in substantially the same plane as that of said universal joint.

13. Irran aircraft va rotating wing assembly ingether and to the drum, said hinges necting said shafts to said drums whereby said drums may be rotated in either direction.

14. In-a rotating wing structure, in combination, a hub, an arm member carried by said hub, a hollow shaft member pivotally mounted on said arm member, a wing storage drum rotatably mounted on said shaft member, a coilable wing attached to said drum, and means carried by said hub and arm member for rotating said drum in either direction upon said shaft member.

l5. In combination, a drum, a fluid-engaging blade, including a large-number of sections hinged together on parallel axes lat widely separated points along its chord, one of said sections being pivotally attached to said drum on an axis parallel to said axes around which drum said blade is adapted to be wound for compact storage.

16. In a rotating wing structure, in combination, a hub, an arm carried thereby, a spindle member pivotally mounted on said arm, a drum rotatably mounted on said member, a coilable wing attached to said drum, and damping means controlling the pivotal movement of the drum on said arm. Y

17. In combination, a rotating wing structure and universal joint means supporting said structure, said structure comprising a plurality of coilable wings and means to which they are pivotally connected, said pivotal connecting means being in substantially the same' plane as the universal joint means. Y

18. In combination, a rotatable arm, a drum, a spindle carrying said drum, said spindle being pivotally mounted on said arm, and drive means including an internal gear in said drum, gears on said spindle meshing therewith, and a spherical central gear meshing with the gears on said spindle. l

19. In combination, a rotatable arm, a drum,

a spindle carrying said drum, said spindle being pivotally mounted on said arm, and interior gearing in the pivotal plane of the spindle for eilecting the drive ofthe drum.

20. In combination, a drum, a wing torsionally i stifi.r and bendable in the direction of its thick- 21. Incombination, a drum, a wing adapted to be coiled thereon comprising a series of rigid sections, and hinges connecting said sections tobeing parallel to the axis of the drum. l

22. 'I'he method o'f making a wing section which comprisesI stamping a sheet of metal to provide adjacent deformations corresponding to top and bottom portions, each of said portions'compfrising a main wall and end wall elements, bending said sheet to bring the ends of the sheet into engagement and the edges of the wall .elements into engagement, welding said extremities together, and welding the engaging end wall elements together.

23. In a section of a multisection rotating wing for aircraft, an integral hollow airi'oilA shell com-` prising an upper member and a lower member integrallyeunited at the forward edge of the section, each of said members comprising an outer wall and end wall portions.' said outer walls beingl welded together to provide the rear edge ofl the of the shell. v

- thickness attached thereto, said sections having- 24. A rotating wingstructure including a drum, a wing composed of a number-of rigid sections hinged together to bend in the direction of their an outer shell of aerofoil form, a reinforcing member within said shell in the vicinity of the greatest thickness of said section, means for winding said wing around said drum in a plurality of layers, and means for causing the surface'of said sections to contact said drum and other said sections substantially at the point of said reinforcement.

25. A rotating wing composed of a number of rigid aerofoil sections, torsionally rigid hinges connecting adjacent sections and maintaining substantial separations therebetween, and compressible material, also of airfoil section, filling said separations with the surface of said compressible material substantially coinciding with the aerofoil contour and forming a continuous wing surface bendable in the direction` of the wing thickness.

26. In a rotating wing, a blade of aerofoil form comprising a number of torsionally stiff sections extending outwardly from a central hub toward the blade tip, a torsionally rigid hinge connecting adjacent sections near the hub across the chord at a plurality of points forwardly from the center of said chord, another similar hinge connecting adjacent sections near the tip, and a plurality of additional similar hinges connecting adjacent sections therebetween, and manually controllable means for causing-adjacent sections to bend relatively to each other to compact said blade adjacent said central hub during rotation of said rotating wing.

27. In a rotating wing, a blade of aerofoil form comprising a plurality of torsionally stiff sections subject to high tension loads due to centrifugal force, each section including a surface member extending around' the front edge of said blade from the top to the bottom thereof adapted to carry both tension and torsional stresses, a plurality of hinge members at opposite ends of each section and connected to the surface memberD in tension communicating relation, the hinge members of adjacent sections being hinged together at a plurality of points from the center of the chord forwardly, and hinge pins means located between the top and bottom surface of said sections and at a substantial distance from adjacent sections to permit substantialbending of adjacent sections in upwardly and downwardly directions 28. In an aircraft, a rotating wing system mounted thereon, a plurality of drums mounted on generally horizontal axes forming a part of said system, an aiifoil section wing comprising a number of rigid sections flexible only in the direction of their-thickness, attached 4at its in ner end to each drum with its chord substantially parallel to the axis of said drum, each said drum comprising means forpreventing twisting about its torsional axis, and means for,A similarly revolving each drum with respect to the wing attached thereto so that each wing is wound up upon its respective drum for compact storage.

29. In an aircraft, a rotating wing system mounted thereon', a plurality of drums mounted on generally horizontal axes forming a part of said system, an airfoll section wing comprising a number of rigid sections flexible only in the direction of their thickness, attached to each drum with its chord substantially parallel to the axis of said drum, means for similarly revolving Y each drum with respect to the wing attached thereto so that each wing is wound up upon its respective drum for compact storage, means for preventing twisting of the wings about their torsional axes, and means for maintaining said wings in at least one partly unwound position.

30. In an aircraft, a plurality of airfoils extending outwardly in a general radial'direction from a central axisaround which they rotate, each airfoil consisting of a series of rigid sections of progressively varying length pivotally connected whereby they may be wound into a coil.

31. In an aircraft, a plurality of airfoils extending outwardly in a general radial direction from a central axis around which they. rotate, the chords of said airfoils lying in the general direction of the plane of rotation, each airfoil consisting of a series of links pivotally connected to tending outwardly in a general radial direction from a central axis around which they rotate, the chords of said airfoils lying in the general direction of the plane of rotation, said airfoils being flexible in the direction perpendicular to their plane of rotation, drum means rotatable about generally horizontal laxes for winding said airfoils into coils in this direction for compact storage, and irreversible drive means for` saiddrum means adapted to lock said airfoils in a partly extended condition.

33. In an aircraft, a drum mounted thereon to rotate around an axis of rotation, said drum having its axis substantially perpendicular to the axis of rotation, a wing including a series of torsionally rigid sections hinged together with hinge axes generally parallel to the'wing chord, means to rotate said drum around the axis of rotation to hold said wing extended by centrifugal force, and means to rotate said drum on its own axis relative to the wing to wind said wing therearound for storage.

34. In combination, an aircraft wing comprising a series of torsionally rigid sections, pivot means connecting said sections together, and a. drum having an axis generally horizontal and parallel to said pivot means to which the inner end of the wing is secured, means to rotate the drum whereby the rotation of the drum on its axis relative to the wing will wind said .wing into a coil around said drum with the chord of the wing substantially parallel to the axis of the drum.

35. In combination, an aircraft wing comprising a series of torsionally rigid sections, a polygornal drum to which the inner end of the Wing is secured, said drum having its axis generally horizontal, said sections being connected together by hinge jointsso that rotation of the drum relative to the wing will wind the wing into a coil around the drum with the chord of the wing substantially parallel to the axis of the drum and the span of the sections lying parallel to the polygonal sides of said drum, and means to rotate the drum.

36. In combination, an aircraft wing comprising a series of torsionallyrigid sections, apolygonal drum to which the inner end of the wing is 1| secured, said drum having its axis generally hori zontal, said sections being connected together by hinge joints so that rotation oi' ,the drum relative to the wing will wind the wing into a coil around the drum with the chord of the wing substantially parallel to the axis ot the drum and 37. A rotating airi'oil system having a blade of airioil section comprising a number of rigid -secalmas-z tions exible only in the direction of their thickness, means permanently. located adjacent the axisof rotation of said rotating airfoil 'system for winding the blade into a coil in a direction of flexibility `around its inner end, means for preventing excessive torsional bending around an` axis in the general longitudinal direction of the blade when extended, said blade being of stable section,lhaving its center of gravity and elastic axis close to its aerodynamic center, and means 10 

